Ian Bogost explains his twisted, Facebook-mocking challenge-less game:
Cow Clicker is a Facebook game about Facebook games. It's partly a satire, and partly a playable theory of today's social games, and partly an earnest example of that genre. You get a cow. You can click on it. In six hours, you can click it again. Clicking earns you clicks. You can buy custom "premium" cows through micropayments (the Cow Clicker currency is called "mooney"), and you can buy your way out of the time delay by spending it. You can publish feed stories about clicking your cow, and you can click friends' cow clicks in their feed stories. Cow Clicker is Facebook games distilled to their essence.
More:
I had formulated some thoughts about why these games bothered me. Whether or not they were "really games" wasn't the issue; I have a long history of defending all sorts of edge cases against that accusation. Nor was it the platform on which they are played; games that use friend networks as infrastructure for asynchronous, social play has long seemed promising to me. . . Rather, I found myself troubled by the way in which these games were games, the manner by which they seemed to magnify the dangerous aspects of games, making those aspects the only ones visible.
Bogost goes on to name these aspects:
ENFRAMING (friends as tools to achieve some end),
COMPULSION,
OPTIONALISM (active effort, as in chess, for example, is optional and gameplay is rote), and
DESTROYED TIME.